Johanna Konta's disappointing run at Grand Slams continued with a comprehensive defeat by sixth seed Caroline Garcia in the US Open heat.
The British No.1 was beaten 6-2 6-2 and has now only won two matches at the last five Slams combined, although this was by far the most difficult draw she has had.
That was a legacy of the fall down the rankings that meant Konta was not seeded at a Slam for the first time since the 2016 Australian Open.
She has shown improved form of late, producing her best two wins of the year by dismissing Serena Williams for the loss of just one game and then defeating former French Open champion Jelena Ostapenko.
But Garcia, who has been heading in the other direction and denied Konta a place at the WTA Finals last year, proved far too strong.
This was their first meeting since Konta won a tight three-set tussle at Wimbledon last summer, and this result was a reflection of how things have gone for both since then.
It was here last year where Konta's dramatic slump began with a shock first-round loss to Aleksandra Krunic.
She did not win another match all season, and on the eve of this tournament opened up about the burn-out that left her feeling unable to compete.
She insisted she is in a much better place now despite her ranking having dropped to 46th, but she was looking for a first win over a top-10 opponent since Wimbledon last year, and Garcia was simply stronger in all aspects.
The Frenchwoman's serve in particular was very impressive, sending down seven aces and denying Konta a break point throughout the match.
Two early double faults did not help Konta and, although her serve and game improved, the damage had already been done as Garcia clinched victory after an hour and 15 minutes.
Caroline Wozniacki opened her campaign with a perfect performance.
The Dane is the highest seed remaining in the women's field after the shock first-round exit of Simona Halep on Monday.
And she laid down an early marker by dispatching former champion Samantha Stosur 6-3 6-2 in a sweltering Arthur Ashe Stadium.
"It's definitely difficult, it's very hot out here," said two-time former US Open finalist Wozniacki. "I just tried to cool down between games and used ice.
"I'm just thinking I'm on the beach, I have a margarita in hand, life is good."
Petra Kvitova of the Czech Republic came back from a break down in the second set to claim a 6-1 6-4 victory over 2009 US Open semifinalist Yanina Wickmayer of Belgium in the first round yesterday.
Kvitova and Wickmayer have had a closely-contested history, with Kvitova holding a slight 5-4 edge, and Wickmayer beat Kvitova en route to the final four at the US Open nine years ago.
But in their first meeting since 2013, Kvitova got the job done, reeling off five straight games from 1-4 down to close out the 71-minute tilt.
No.4 seed Angelique Kerber got her campaign underway, fighting past an in-form Margarita Gasparyan in two sets in her opening round match.
On a balmy day at the Louis Armstrong Stadium, Kerber had to recover from a break deficit in both sets to score the 7-6 (5) 6-3 victory in one hour and 45 minutes.
"It was not easy today, it was so hot," said Kerber in a courtside interview after the win.
"I'm very happy to get through, I just wanted to play point by point and not think too much.
"Despite the conditions it was good match and both of us were at a high level."
Up next, Kerber will take on Johanna Larsson in the second round. The Swede came back from a set down to knock out Alize Cornet, 4-6 6-3 6-2.
No.10 seed Jelena Ostapenko weathered a mid-match letdown - and tough weather conditions against a motivated opponent - to knock out Andrea Petkovic in three sets, 6-4 4-6 7-5.